Method of manufacturing a lamp

ABSTRACT

A method of providing a rigid support for the filament structure during the manufacturing of electric lamps with envelopes having at least one pinch seal, by temporarily securing fusible metal connection rods directly to the current lead-in members within the envelope. After the lamp assembly has been sealed, short circuit current having sufficient intensity for melting the connecting rods is passed through the lamp to eliminate the temporary short circuit between the lead-in members.

United States Patent [191 [111 3,817,591 Deiss June 18, 1974 METHOD OF MANUFACTURING A LAMP [56] References Cited [75] Inventor: Claude Joseph Charles Deiss, UNITED STATES PATENTS Asmeres, France 3,270,237 8/1966 Danko 313/220 Assigneea F iq R i d 3,271,093 9/1966 Meier 3l6/l9 Electriques, lssy-les-Moulineaux (Hauts de Seine), France Primary Examiner-Roy Lake Assistant Examiner-J. W. Davie [22] Filed 1972 Attorney, Agent, or Firm-Frank R. Trifari [211 App]. No.: 315,645

Related US. Application Data ABSTRACT [63] Continuation of Ser. No. 164,961, July 21, 1971, A method of providing a rigid support for the filament abandoned which Is a commuatlon of structure during the manufacturing of electric lamps 813,114 1969 abandmedwith envelopes having at least one pinch sea], by temporarily securing fusible metal connection rods di- [30] Forelgn Apphcatlon Pnomy Data rectly to the current lead-in members within the enve- Apr. 11, 1968 France 68.147774 lope, After the lamp assembly has been sealed, short circuit current having sufficient intensity for melting [52] US. Cl 316/19, 29/25.l5, 31 3/27l the connecting rods is passed through the lamp to [51] Int. Cl. H01] 9/ 18 eliminate the temporary short circuit between the [58] Field of Search 29/25.l3, 25.15, 25.16; lead-in members.

1 Claim, 3 Drawing Figures PATENTEBJIII 10 1914 fig.

11. 1 5 fig.2

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AGENT 1 METHOD OF MANUFACTURING A LAMP This is a continuation of application Ser. No. 164,961, filed July 21, I971; which is a continuation of Ser. No. 813,114, Apr. 3, 1969, both of which are now abandoned.

The invention relates to a method of manufacturing a lamp vessel provided with at least one pinch seal and destined for an electric filament lamp, in which pinch seal at least two pole wires are sealed between which one or more electric filaments are stretched.

In manufacturing such electric filament lamps, a quartz glass tube which is open at both ends is frequently used as the starting material. A few pole wires between which one or more filaments are stretched are arranged inside said tube in the prescribed manner, after which a part of the tube which is made flexible by heating is pinched around the pole wires.

These pole wires are formed from a few parts which are secured together axially and comprise, at least at the region of the pinch seal, a part of a very small diameter, for example, of the order of a few tens of microns. Only then can this part be sealed to the glass in a satisfactorily vacuum-tight manner. The envelope in question always comprises, at its end remote from the pinch seal, an exhaust tube through which members can be provided with diffilculty only for fixing the position of the filaments in the envelope. It is therefore necessary to hold the pole wires, or parts thereof which are situated outside the lamp vessel, near the pinch. Since these parts to be sealed have a very small diameter, it will be obvious that it is substantially impossible to support the internal pole wire parts in such manner that the filaments in said lamp vessel afterwards assume a prescribed position.

It is known to compensate for this lack of rigidity by permanent, electrically insulated, rigid connections which, inside the envelope and beyond the melting region, form part of the current conductors. These connections must maintain the electric insulation between the current lead-in members and therefore they are manufactured either in a monolithic form by means of non-conductive material, or in the form of a chain of elements of which at least one is insulating. Glass beads through which the metal wires are threaded form an example of such a chain.

However, these methods have various drawbacks. The insulating elements must be sufficiently refractory to withstand high temperatures when they are situated in the proximity of the melting region; the materials used require a very careful and hence expensive operation (working temperature, brittleness in the case of shocks); due to their importance, said factors may adversely influence the good mechanical behaviour of the assembly. The commonly used materials (porcelain, mica, hard glass), may contaminate the atmosphere of the space, which is often carefully checked, by giving off gas and vapour at high temperatures. In certain cases, even the dissociation temperature of the material may be reached.

Due to the method according to the invention, said drawbacks can be avoided by replacing the insulating permanently secured elements by temporary metal connections which are welded directly to the current lead-in members. The connections play a mechanical part during mounting and sealing after which they are removed by melting. This melting is obtained by conveying through the connection a current of a sufficient intensity to heat the connection until it fuses (locally melts and breaks the current) and this by means of the current lead-in members themselves.

In order to fulfil these requirements and to fulfil the temporary connection function, the connection must have dimensions which mainly depend upon the desired regidity, on the permitted intensity of the melting current in the current lead-in members and the intermediate members and upon the nature of the material used.

In order that the invention may be readily carried into effect, two examples thereof will now be described in greater detail, by way of example, with reference to the accompanying drawing. The drawing shows a filament lamp having two filaments which can be operated separately or simultaneously.

FIG. 1 is a longitudinal cross-sectional view.

FIG. 2 is a cross-sectional view taken on the line "-1! of FIG. 1.

FIGS is a variation of FIG. 1.

The envelope 1 of the lamp shown in FIG. 1 consists of quartz glass. The lead-in members 2, 3 and 4 support andsupply the two filaments 6 and 7; the lead-in members each consist of three parts: rigid parts 2, 3, 4 inside the envelope, rigid parts 9, 10, l 1 outside the envelope, and flexible parts 13, 14, 15 each formed as a ribbon of molybdenum of approximately 25 microns thickness. Only the rigid exterior parts can be held during the formation of the pinch 5. During sealing, which is carried out at a high temperature in the region 5, the location of the intermediate parts and the interior parts which support the filaments 6 and 7 cannot be ensured in the correct manner by pinching; the position of these two filaments with respect to each other and with respect to the axis of the envelope is determined with small tolerances in the order of 0.3 mm.

The distance between the current lead-in members can be maintained during assembly and sealing by welding a tungsten rod 8, diameter approximately 0.2 mm, to the interior rigid parts 2, 3 and 4 of the current lead-in members.

When the assembly is sealed, the lamp is evacuated through the exhaust tube 12, filled with a neutral gas and successively or simultaneously a voltage is applied between the current lead-in members 9, l0, and 11 which is sufficient to melt the rod 8, the cross-sectional area of the rod is greater than the cross-sectional area of the filaments to provide a low resistance path across the filaments; a simple electric device interrupts the contact when the intensity falls below a given value, that is to say as soon as the connection rod 8 has fused (locally melted and interruped the current).

In the example described it is even possible to finish the Iarnp without fusing the connection. Fusing occurs automatically when the lamp is operated for the first time. This is possible only when the normal operating voltage of the lamp is sufficiently low to prevent the formation of an arc.

By the passage of the melting current through the lead-in members the quality of the electric welds between the elements of the current lead-in members can be checked which welds are interrupted when the quality is insufficient.

In the variation shown in FIG. 3, the more rigid and hence more efficaceous connection system is used consisting of the parallel arrangement of two rods 16 and 17 of the same diameter which is smaller than that of the single rod shown in FIG. 1. This manner of mounting avoids any twist of the lead-in members about the welds on the connection.

The method which has just been described for an electric lamp having flexible lead-in members may be applied in all cases in which a location of elements relative to each other is to be ensured in a space which is not readily accessible and in which this location cannot be ensured with sufficient accuracy during the total or partial sealing of the space; all this in a manner difiering from supports placed between the elements.

This means that the application of said method can be considered for the manufacture of a variety of products to improve the accuracy of assembling and the quality of the product or to reduce the cost of the operations.

What is claimed is:

1. A method of manufacturing an electric lamp having at least two pole wires, said pole wires supporting an electric filament streached therebetween, comprising in sequence the following steps: welding at least one heat fusible electrically conducting connection rod to said pole wires at locations thereof to provide rigid support for said pole wires and filament, said rod having a cross-sectional area greater than the cross-sectional area of said filament to provide an electrical circuit of low resistance in parallel with the high electrical resistance circuit of said filament, mounting said pole wires and sealing one end of the envelope of said lamp thereby to embed said pole wires within the envelope of said lamp, evacuating and sealing said lamp, energizing current lead-in members of said lamp to electrically heat and thereby melt said rod thereby eliminating the fusible support between said pole wires.

l l IIR 

1. A method of manufacturing an electric lamp having at least two pole wires, said pole wires supporting an electric filament streached therebetween, comprising in sequence the following steps: welding at least one heat fusible electrically conducting connection rod to said pole wires at locations thereof to provide rigid support for said pole wires and filament, said rod having a cross-sectional area greater than the cross-sectional area of said filament to provide an electrical circuit of low resistance in parallel with the high electrical resistance circuit of said filament, mounting said pole wires and sealing one end of the envelope of said lamp thereby to embed said pole wires within the envelope of said lamp, evacuating and sealing said lamp, energizing current lead-in members of said lamp to electrically heat and thereby melt said rod thereby eliminating the fusible support between said pole wires. 